This study aimed to explore whether recording of a prior adverse pregnancy outcome (postpartum hemorrhage) in a medical record increases the likelihood that recurrence of the same event is reported in hospital data. Using a sample of 588 pregnancies [2 consecutive pregnancies for 294 randomly selected women with at least one postpartum hemorrhage (PPH)], we compared 'coded' recurrence rates in hospital data with those obtained from medical record audit. 'Coded' recurrence in a second pregnancy was also compared for women with or without a documented history of prior PPH. We found a 'coded' recurrence rate of 18.5% and an 'audited' recurrence rate of 28.4%. The 'coded' rate of recurrence among women who had a documented history of PPH was 27.4% compared to 19.1% when the previous PPH was not noted in the second pregnancy medical record. Medical record reporting of uterine atony as the cause for postpartum hemorrhages in first and second births was 37.9 and 34.0% while 'coded' hospital data reporting attributed 79.8 and 73.9% respectively to atony. Our study results indicate that a history of postpartum hemorrhage may be a stronger risk factor for subsequent PPH than previously demonstrated. A recorded history of PPH was associated with an increased likelihood of reporting a subsequent PPH, and in such cases recurrence rates approximate true recurrence. The contribution of uterine atony as a cause of postpartum hemorrhage is over-estimated using hospital data.